diff --git a/db/db.go b/db/db.go
index 86d1bec3c..3300727f5 100644
--- a/db/db.go
+++ b/db/db.go
@@ -13,6 +13,7 @@ type DB interface {
 	SetSync([]byte, []byte)
 	Delete([]byte)
 	DeleteSync([]byte)
+	Close()
 
 	// For debugging
 	Print()
diff --git a/db/mem_db.go b/db/mem_db.go
index 9b9b0d207..b7d8918d4 100644
--- a/db/mem_db.go
+++ b/db/mem_db.go
@@ -33,6 +33,10 @@ func (db *MemDB) DeleteSync(key []byte) {
 	delete(db.db, string(key))
 }
 
+func (db *MemDB) Close() {
+	db = nil
+}
+
 func (db *MemDB) Print() {
 	for key, value := range db.db {
 		fmt.Printf("[%X]:\t[%X]\n", []byte(key), value)